Steel pipe is commonly used in the oil and gas industry. This type of pipe may be used in the transport of fluids to or from the well such as oil and gas gathering lines, flow lines, and fluid and gas injection lines which may be installed on the surface or buried. Steel pipe may also be used for downhole applications such as drilling, intervention, or production including drill strings, coiled tubing, production tubing, casing, and velocity and heater strings, and the like. Carbon steels, however, may be susceptible to corrosion by oilfield fluids, such as produced or injected water, brine, and dissolved acids from CO2 or H2S, as well as well work-over fluids such as HCl and HF. Furthermore, steel pipelines, gathering lines or injection lines are usually installed using short (30-40 foot) sections. This requires additional labor and provides the possibility for fluid leakage at each fitting. Such labor intensive installation may also lead to lost revenues if production or transport of the fluids is suspended during the installation.
To resist internal corrosion, steel alloys, non-metallic internal coatings, or fiberglass-reinforced epoxy pipe may be used, but all may still have the disadvantage of being sectional products. In addition, the wall of a fiberglass-reinforced epoxy pipe may be fairly damage intolerant and may require careful handling, installation, and/or use of specific back-fill materials. Damage or cracks in the fiberglass-reinforced epoxy layer can, in some cases, lead to small leaks or “weeping” of the pipe under pressure. In some applications, thermoplastic liners may be used as corrosion protection inside steel pipe, but these liners are susceptible to collapse by permeating gases trapped in the annulus between the liner and the steel pipe if the pressure of the bore is rapidly decreased. Unreinforced thermoplastic pipe, on the other hand, can usually only tolerate relatively low pressures especially at elevated temperatures and in the presence of oilfield fluids.
Thermoplastic lined fiberglass pipe designed for relatively moderate pressure, for example, 0 to about 500 PSI service may have thin walls that may be damage intolerant or may kink or collapse when spooled at moderate spooling strains of about 1-10%. High modulus materials such as epoxies may increase the tendency for the thin-walled pipe to kink or collapse. Materials such as Kevlar may used for reinforcement but may be prohibitively expensive for many applications. Bare fiberglass reinforcement of, for example, a thermoplastic liner may be susceptible to corrosion by water, especially in the presence of dilute acids, bases, or stress. Abrasion of bare fibers against each other during manufacturing, spooling, installation, or operation may cause breakage of glass fibers and reduction of hydrostatic strength. Uneven surfaces of the fibers against a tube liner may cause point loading; gouging of the fibers into the liner may increase the tendency to stress cracking of the liners; individual fibers that can move independently may spread so as to allow the liner to extrude past the fiber reinforcement and rupture. Therefore, there is a need for a low-cost, corrosion resistant, spoolable, reinforced inner-lined pipe for such relatively low pressure applications that is damage tolerant and will not kink when spooled.